1. Field of the Invention
The present invention relates to a sheet receiving and stacking apparatus for receiving and stacking plastics sheets and other kinds of paper which are rectangular sheets and, more particularly, is applicable to a delivery apparatus in an image forming apparatus such as a printing apparatus.
2. Description of the Related Art
Generally, as a sheet receiving and stacking apparatus for receiving and stacking rectangular printed sheets, a delivery apparatus provided at the discharge section of a printing apparatus has been known. This type of delivery apparatus 1, as shown in FIG. 1, commonly has a base table 6 for receiving printed paper 3, a pair of parallel side boards 4, 4 provided generally vertically on both sides of the base table 6 in a direction in which the paper 3 is received, and an end plate 5 provided at the forward end of the base table 6 in the direction of reception of the paper 3. Both side edges of the paper 3 ejected from the printing section of the printing apparatus 2 are received between two side boards 4, 4 which are disposed parallelly, generally equal to the width of the paper 3. The leading edge of the ejected sheet 3 strikes the end plate 5 located at front and floats down to the stack section on the base table 6.
In such a delivery apparatus 1, in the case of printing of a low printing rate on the paper 3, that is, in the case of a small amount of printing ink to be transferred to the paper 3, the paper 3 is discharged out of the printing apparatus 2 without changing its flat form; therefore there will occur no problem about the stacking of the paper 3 in the delivery apparatus 1. However, in the case of a high printing rate, for example when a large amount of ink has been transferred to the paper 3 as in solid printing, the upper surface of the paper 3 to which the ink has been transferred extends largely, curling largely downwardly into an upwardly swollen form on the whole. The paper 3 discharged from the printing apparatus, therefore, will be stacked in a disorderly fashion on the base table.
To solve this problem, there has been a printing apparatus 7 of known art that, as shown in FIG. 2, is provided with an auxiliary paper discharge member 8 at the inlet of the delivery apparatus 10 mounted in the paper delivery section. This auxiliary member 8 holds upwardly both side edges of the paper 9 in a direction of travel of the paper 9 discharged from the printing apparatus 7, so that the paper 9 is bent into a form of U letter in the delivery state to thereby provide the paper 9 with stiffness and thereby prevent the paper 9 from being largely curled with the effect of ink and stacked on the delivery apparatus 10 in a disorderly fashion.
Another apparatus which curves the paper into a U-letter form has been disclosed in Japanese Utility Model Laid-Open No. Hei 5-10367. This apparatus has a pair of side plates so disposed as to face each other at a spacing on the delivery table, a pair of guide members provided on the pair of side plates so disposed as to face each other and protrusible on the delivery table, and guide members driving means for driving the guide members by turning the guide members in synchronism with the delivery of the image forming apparatus.